Abstract
The main purpose of this study was to investigate the solubilization enhancement properties of an amphipathic graft copolymer, Soluplus®, on test compounds. Micellization of Soluplus® in solution was characterized by evaluating the changes in the surface activity, turbidity, and thermodynamic behavior. To assess the feasibility of Soluplus® as a polymeric carrier of solid dispersions, freeze-dried samples of ipriflavone were prepared, and the physicochemical properties of the carrier plus ipriflavone were evaluated in terms of solubility, dissolution, and crystallinity. The surface tension of the solution decreased depending on the polymer concentration, and gradual turbidity increase was observed. Isothermal titration calorimetry was used to measure the thermal reaction accompanying the micellization of Soluplus® and indicated that a colloidal micelle formation improved solubility. The prepared formulations, particularly at a ratio of ipriflavone : Soluplus®=1 : 10 (w/w) exhibited a dramatically improved solubility of ipriflavone that was ca. 70-fold higher than that of untreated ipriflavone. The solubilization mechanism of Soluplus® was partially elucidated and suggested that its strategic application could improve the solubility of hydrophobic compounds.
